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Reference to Microfiche Appendix
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1. Field of the Invention
This invention relates generally to interconnection systems and more specifically to high speed interconnection systems.
2. Description of Related Art
Interconnection systems are used in modern electronic systems to route signals from one electronic component to another. Most modern electronic systems are manufactured from many integrated circuit chips. The chips are mounted to printed circuit boards, which route electric signals between the integrated circuit chips or between the integrated circuit chips and other parts of the system.
Many electronic systems, such as computer servers or telecommunications switches are built using printed circuit boards configured as a backplane and multiple xe2x80x9cdaughterxe2x80x9d cards. In such a configuration, the active circuitry of the electronic system is built on the daughter cards. For example, a processor might be built on one daughter card. A memory bank might be built on a different daughter card. The backplane provides signal paths that route electrical signals between the daughter cards.
Generally, electrical connectors are mounted to both the backplane and the daughter card. These connectors mate to allow electrical signals to pass between the daughter card and the backplane.
Because the electronic systems that use a backplane-daughter card configuration usually process much data, there is a need for the electrical connectors to carry much data. Furthermore, this data is generally transmitted at a high data rate. There is simultaneously a need to make the systems as small as possible. As a result, there is a need to have electrical connectors that can carry many high speed signals in a relatively small space. There is thus a need for high speed-high density connectors.
Several commercially available high-speed, high density electrical connectors are known. For example, U.S. Pat. No. 6,299,483 to Cohen et al. entitled High Speed High Density Electrical Connector is one example. Teradyne, Inc., the assignee of that patent, sells a commercial product called VHDM(copyright). Another example may be found in U.S. Pat. No. 6,409,543 to Astbury, et al. entitled Connector Molding Method and Shielded Waferized Connector Made Therefrom Teradyne, Inc., the assignee of that patent, sells a commercial product called GbX(trademark). The foregoing patents are hereby incorporated by reference.
One of the difficulties that results when a high density, high speed connector is made in this fashion is that the electrical conductors can be so close that there can be electrical interference between adjacent or nearby signal conductors. To reduce interference, and to otherwise provide desirable electrical properties, metal members are often placed between or around adjacent signal conductors. The metal acts as a shield to prevent signals carried on one conductor from creating xe2x80x9ccross talkxe2x80x9d on another conductor. The metal also impacts the impedance of each conductor, which can further contribute to desirable electrical properties.
The shielding in an interconnection system can never be perfect. Often, the design of the interconnection systems reflects a compromise between the level of shielding that can be achieved and other system requirements. For example, it is often necessary for the interconnection system to have a limited size or to be made in separate pieces that can be disconnected or to be manufactured below a certain cost.
As signal frequencies increase, the risk of crosstalk or other undesirable electrical properties in an interconnection system increases. It would be desirable to provide an improved interconnection system for high frequency signals.
As will be described below, we have invented a system that uses radiation absorptive materials. Use of absorptive material is known in high frequency systems, such as in packages that contain microwave components. However, we do not believe that the prior art has recognized the benefits or application of absorptive material in interconnection as described below.
With the foregoing background in mind, it is an object of the invention to provide an improved interconnection system for high frequency signals.
To achieve the foregoing object, as well as other objectives and advantages, an interconnection system is provided with electromagnetic absorptive members positioned to preferentially absorb unwanted radiation.
In a preferred embodiment, the electromagnetic absorptive members are ferromagnetic materials.
In one embodiment, the interconnection system is a high-speed, high-density electrical connector. In other embodiments, the interconnection system is a printed circuit board.
In another embodiment, material with a high magnetic or electric loss tangent is built into a multi-ground interconnect structure to reduce unwanted modes of electromagnetic energy. Preferred embodiments of the multi-ground interconnect structure are an electrical connector, a circuit board and a cable.